Method of and apparatus for testing gases



Oct. 16, 1934.

' G. JONES 1,977,481

METHOD OF AND APPARATUS FOR TESTING Filed Aug. V28 .1950

WITNESSES i as I l I l E274 fire hazards.

Patented Oct. 16, 1934 lama ATENT METHOD OF AND APPARATUS FOR TESTING GASES George W. Jones, Pittsburgh, Pa.

Application August 28,

.. T 17 Claims.

This invention relates to gas testing, and especially to a method of and apparatus for determination of the explosibility of a gas.

The atmosphere in sewers, manholes, mines,

' 6- underground conduits, and similar places is often dangerous, either because of an oxygen deficiency, or else because of a content of a flammable or explosive constituent. Accordingly, such atmospheres present both respiration and explosion or It is desirable therefore to test such atmospheres periodically, either to reduce the liability of fire or explosion, or else as a safety measure before workmen or other persons are exposed to them. However, up to the present I51 time no means has been available for quickly ascertaining an oxygen deficiency or the approximate explosibility of such gases,which was readily portable, simple and reliable in operation, and operable by persons not having scientific train- 20 ing.

An object of this invention is to provide a method oftesting a gas to determine whether it contains a flammable constituent, or whether there r is an oxygen deficiency, which is simple, readily performed, does not require delicate or complicated apparatus, and which quickly and readily gives information whether a flammable constituent is present within, above, or below explosive limits, or whether there is an oxygen deficiency.

A further object of the invention is to provide an apparatus for use in connection with the process referred to, which is rugged, simple, does not requireskill in its operation, is adapted for I field use, and which quickly gives the desired information.

' The invention may be described in connection with the accompanying drawing, in which Fig. 1 is a front elevation of an apparatus embodying the preferred construction; Fig.2 an elevation 40 of the left hand side of the apparatus shown in Fig. l; and Fig. 3 a wiring diagram of the apparatus shown in Figs. 1 and 2.

In testing the explosibility of gases four conditions may exist, in that a flammable constit- 4 5 uent may be present, (1) within the explosive under atmospheric pressure, and it is exposed tov ignition. If explosion occurs, there is present in the gas a flammable constituent within the ex- 1930, Serial No. 478,523

plosive range, and the desired information is had at once.

If the sample is not initially explosive, then any of conditions 2, 3, or 4 may prevail, and in accordance with the invention this is determined by incrementally varying the composition of the gas by displacing successive measured portions of the sample with like amounts of a combustion-induc-' ing gas, and exposing the mixtures to ignition, until an explosive mixture is formed or an amount of the combustion-inducing gas equivalent to or slightly above its lower explosive limit value in air has been added.

In the practice of the invention the presence of a flammable constituent in a concentration below the lower explosive limit is determined by incrementally enriching it with a combustible gas. If an explosive mixture is formed by the incremental variation above referred to, then the gas containsa flammable constituent in an amount not less than 100 minus the total percentage of explosive'nessof combustible gas added. Thus, if anamount of combustible gas equivalent to 25 per cent of its lower explosive limit value is added, and the enriched mixture is explosive, then the original sample is not less than per cent explosive.

If an explosive mixture is not obtained after a fully explosive concentration of combustible gas has been added, the original sample is either nonexplosive, due to an oxygen deficiency, or else the concentration of any flammable constituent which maybe present is above the upper explosive limit. In order to determine which of these two conditions exists, a fresh sample is tested for initial explosiveness, as before, after which the sample is progressively diluted with incremental amounts of an oxygen-containing gas, and the thus diluted samples are exposed to ignition. This incremental dilution and exposure to ignition is repeated until explosive combustion results, which proves the'presence of a flammable constituent above the upper explosive limit, or else until 100 per cent of the oxygen-containing atmosphere has been added. If explosion has not taken place upon the addition of 100 per cent of the oxygen-containing atmosphere, which in this case forms the combustion-inducing gas, then the original gas is substantially free from a flammable constituent, and an oxygen deficiency is 105 indicated.

Any suitable combustible gas may be used in the practice of the invention, such, for example, as carbon monoxide, those'being preferred which maybe liquefied and. which have a high vapor 110 pressure at normal temperatures. In the preferred embodiment of the invention, however, a combustible parafiin hydrocarbon is used, and most suitably propane, which is new commercially available in liquid. form in small cylinders. Air is preferably used as the oxygen-containing gas. Most suitably, ignition of the gas samples and mixtures is eifected by means of a spark generated within the sample. The incremental replacements, either of combustible gas or of oxygen-containing gas, may be of any desired value. For most purposes increments of the combustible gas corresponding to 25 per cent of the explosive limit of the gas with air will aiford satisfactory results when enriching a sample with combustible gas; and increments of oxygen-containing atmosphere equivalent to approximately one-fourth of the total volume of the original sample are satisfactory in dilution of a sample.

Because both the combustible gas and the oxygen-containing gas cause combustion of mixtures when a flammable constituent is present is an amount either below or above the explosive limits, such gases are, for brevity or reference, herein designated as combustion-inducingv gases.

The apparatus provided by and preferably used in the practice of the invention comprises a gas sample container adapted to withstand explosive combustion of a sample of gas contained therein, which is provided with valvedinlet and outlet connections, meansforigniting a sample of gas, and also with means for indicating the occurrence of combustion. The apparatus is also provided with a gas measuring element for replacing a measured portion of sample with a' standard amount of combustion-inducing gas.

Having reference to the drawing, the apparatus comprises a cylindrical bomb 1 provided with valved inlet and outlet connections preferably in the form of stopcocks 2 and 3 respectively. The bomb is provided with a pressuregauge 4, preferably of the drag needle type, and with gas igniting. means, such as a spark plug 5 threaded into the body of the bomb and connected to a spark coil 6 mounted within a case 6a, Fig. 2.

The apparatus is also provided with meansfor varying the composition of a sample by means of a standard measured amount of combustion-inducing gas. In the preferred embodiment this element comprises a tubular member or nipple '7 provided at one end with a valved connection 8 to the atmosphere, and a valved connection 9 connected to outlet 3. At the other end memher 7 is provided with branched valves 10 and 11, the former being connected by means of pressure tubing 12 to a source of combustible gas, such as a cylinder 13 of compressed propane. It will be seen that by closing valves 9 and 11 and permitting gas to flow through valve 10, tube 7 and valve 8, followed by closing valves 8 and 10, a fixed amount of gas under atmospheric pressure may be measured for addition to a sample in the bomb.

Inlet valve 2 is provided with a length of fiexible tubing 14 connected to the outlet side of an aspirator bulb 15 whose inlet side may be connected to tubing 16 for insertion into an atmosphere which is to be tested.

In the use of this apparatus, valves 8 and 10 are closed, and valves 2, 3, 9 and 11 are opened. Tubing 16 is inserted into the atmosphe're'which isto be tested, such as a manhole, and aspirator bulb 15 is squeezed a sufiicient number of times to sweep the air from the tubing 16 and 14, bomb 1, and member 7 out through valve 11. When this has been accomplished the aspirator bulb is disconnected from tubing 16 and its inlet side is connected to a length of tubing 18 associated with branch 11, so that a sample of the atmosphere under test is trapped in a closed system under atmospheric pressure.

Valves 2 and 3 are now closed, whereby a portion of the sample is enclosed within bomb 1. The spark circuit isthen closed, and if the sample is an explosive mixture the needle of gauge 4 will indicate a sudden rise in pressure.

If no explosion occurs the gas is not explosive itself. Valves 8 and 10 are then opened, and valve 17 on cylinder 13 is opened to permit combustible gas to flow through tubing 12 and gas measuring element 7 into the atmosphere from connection 8. In order to render the flow of combusti'on-inducing gas visible and to trap a definite volume in member '7 at atmospheric pressure, a short length of rubber tubing connected to valve 8 is dipped into water or other suitable liquid held in a cup 26. As soon as the combustion-inducing gas has displaced the gas being tested from this part of the system, valve 17 is closed, after which valves 8 and 10 are closed. Valves 2, 3, 9 and 11 are now opened and the bulb is. squeezed a number of times to induce thorough mixing of the sample with the measured portion of combustible gas by circulating them through the bomb, nipple '7, and tubing 14 and 18. All of the valves are then closed, and a spark is again caused topass within the bomb. In the preferred embodiment of the apparatus the gas measuring element is selected of such size that the charge of combustible gas represents an amount equivalent to 25 per cent of its lower explosive limit with air when mixed with the original sample.

. If an explosion occurs, as indicated by movement of the pressure gauge needle, it shows that the original sample was not less than 75 per cent explosive, since the added measured volume of combustible gas is equivalent to 25 per cent of an explosive gas-air mixture. If, on the other hand, no explosion results, the foregoing procedure is repeated, whereby combustible gas equivalent to per cent of an explosive mixture is added, and if no explosion then occurs, the incremental enrichment is repeated until combustible gas equivalent to 100 per cent of explosive mixture has been added. If after the fourth addition of combustible gas no explosion has taken place, then the original sample is above the upper explosive limit, or else it is nonexplosive due to an oxygen deficiency. g

The occurrence of an explosion after the first addition shows that the original sample is not less than per cent explosive. Likewise, explosion after the second addition indicates that the original sample is not less than 50 per cent explosive, and similarly it is not less than 25 per cent explosive if explosion occurs after the third addition. If explosion does not occur until after four additions of combustible gas, theoriginal sample is less than 25 per cent explosive.

In order to determine Whether the gas is deficient in oxygen, or whether the concentration of flammable gas is above the upper explosive limit, valves 2, 3, 9 and. 11 are opened,'aspirator bulb 15 is disconnected from tubing 18 and again connected to tubing 16. The apparatus is again swept out by repeated compression of thebulb, and when the system contains only the gas to be tested, which is usually effected after about twenty-five squeezes of the-bulb, valves 2, 3, 9

and 11 are closed, and. the sample is again tested for initial explosibility, to check the first result. If no explosion occurs, the aspirator bulb is disconnected from tubing 16, valves 2, 3, 9 and 11 are opened, valves 8 and remaining closed, and the bulb is given two squeezes, which thereby displaces a portion of the sample with an amount of air equivalent to twice the volume of the aspirator bulb. Aspirator bulb 15 is again connected to tubing 18 and squeezed to mix thoroughly the introduced air and sample, twenty-five squeezes being usually sufficient. The valves are again closed, and the thus diluted sample is exposed to ignition by closing of the spark circuit. This procedure is repeated until movement of the needle of gauge 4 indicates that combustion has taken place, or until the sample has been replaced by air.

In the preferred embodiment the aspirator bulb is chosen so that each addition represents substantially one-fourth of the total volume of gas contained inthe bomb aspirator bulb and connections, so that after eight individual additions the sample will have been largely replaced by air. An explosion after any addition shows that a flammable constituent was present above the upper explosive limit. If explosion has not occurred after eight additions of air (with the bulb referred to), then the sample contains so much inert gas that the mixture is non-explosive, and an oxygen deficiency is indicated.

Where the appartus is used with atmospheres which are combustible, it is advantageous to so construct it that a spark will not be prematurely formed, as otherwise combustion of the gas prior to closure of valve 2 might cause a flash back into the .source of the gas. In the embodiment shown this is accomplished by means of a supplement sw1tch associated with valve 2 in such manner that the spark circuit is always open until this valve is closed. As shown in Fig. 3, the primary of coil 6 is connected by a conductor 18 to batteries 19, and the secondary is connected to spark plug 5 by a conductor 180.. A switch 30 is inserted in the primary circuit. The supplemental switch comprises a metallic strip 21, Figs. 2 and 3, mounted on the end of the stem of valve 2, in such position that when the valve is open the spark circuit is broken, this position being indicated in dotted lines in Fig. 3. When valve 2 is closed, auxiliary switch plate 21 connects switch points 2101., so that the circuit may be closed. by switch 20. In this manner, switch may be closed, but until valve v2 has been closed the circuit will be open and it will not be possible to cause a spark to pass within the bomb.

In order to be readily portable; the apparatus is preferably mounted upon a rigid frame 23. It

i may at times be desirable to carry the sample container to some point remote from the mounting which carries the balance of the apparatus, in order to draw a sample. In order to accomplish this, bomb 1 is mounted upon a bracket member 24, and outlet 3 is connected to valve 9 by a coupling 27, whereby it is readily detachable and may be lifted bodily from the apparatus. When so used, valves 2 and 3 are opened, and the sample is taken at any desired point by aspiration of bulb 15,-and when the air has been displaced from the-bulb, tubing and bomb and replaced by a sample of the gas, valves 2 and 3 are closed, and the bomb is replaced in the apparatus and coupling 25 connected, after which I the procedure is as described above.

The invention thus provides means for readily and. quickly getting information as to the character of a gaseous atmosphere. The method may be practiced and the apparatus used with equal facility, and to obtain equally reliable results, by unskilled workers as well as by those having scientific experience. The apparatus is portable, so that the invention maybe practiced anywhere, and not only is the information quickly had, but it gives a positive determination of the fire, explosion or respiratory hazard of the atmosphere in question, and through the use of the invention accidents maybe avoided.

According to the provisions of the patent statutes, I have explained the principle and mode of operation of my invention, and have'illustrated and describedwhat I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and de-' scribed.

I claim:

1. In a method of testing a gas to determine its explosibility the steps comprising exposing to ignition a sample of said gas confined in a closed system, and'if the gas does not explode, successively admixing with it measured incremental amount of a combustible gas and exposing the enriched mixture to explosion, and if the thusenriched mixture does not explode repeating such enrichment until explosion occurs or per cent of an explosive concentration of said combustible gas has been added.

2. In a method of testing a gas to determine its explosibility the steps comprising exposing to ignition a sample of said gas confined in a closed system under atmospheric pressure, andif the gas does not explode, successively displacing incremental volumes of said gas with equal measured volumes of a combustible gas and successively exposing each. of the thus-enriched mixtures to ignition until explosion occurs or the amount of said combustible gas added is equivalent to its lower explosive limit in air.

3. A method of testing a gas according to claim 2 in which a paraflinhydroca'rbon gas is used as the enriching combustible gas.

4. A method of testing a gas according to claim 2 in which propane is used as the combustible gas. I

5. In a method of testing a gas to determine its explosibility the steps comprising confining a sample of said gas under atmospheric pressure in a closed-system, exposing the, sample to spark ignition, and if explosion does not occur, admixing with the sample a measured volume of a combustible gas while maintaining atmospheric pressure in the system, exposing the thus-enriched mixture to ignition, and if the thus-enriched mixture does not explode repeating such incremental enrichment and exposure to ignition until ignition occurs or 100 per cent of an explosive concentration of said combustible gas in air has been added.

6. In a method of testing agas to determine its explosibility the steps comprising confining a sample of the gas to be tested under atmospheric pressure in aclosed system, exposing the sample to ignition, if ignition does not occur, replacing aportion of the sample with an equal measured volume of a combustible gas equivalent to 25 per cent of the lower explosive limit of said combustible gas in air, and exposing the enriched mixture to ignition, and if said mixture does not ignite successively repeating such incremental enrichment, and exposure to ignition untilan explosive mixture is obtained or'100 per cent of combustible gas has been added; v h

7. A meth'odjof testing gas accordingtoclaim 6 in whichpropane is used as the combustible gas. 8. A method of testing. a gas according'to claim 15 in which air is used asthe oxygen: containing gas. f I

9. Apparatus for determining the explosibility of a gas comprising a gas sample container of predetermined volume adaptedto withstandexplosive combustion of a gasiconfinedtherein and provided with a pair of closable line connections, spark-producinguneans disposed "within said container for producing a spark therein, and combustion-responsive means associated with said container for indicating the occurrence of combustion therein; .agas-measuring jmember adapted to be connected to a source and to measure afixed amount of combustion-inducing gas, and connections between said memberand container for circulating and mixing said sample and measured amount of combustion inducing ,10. Apparatus for determining the explosibili tyof a gas comprising a gas sample cylinder of predetermined volume adapted to withstand explosive combustion of a sample of gas confined therein, valved connectionsassociated'lwith the ends of said cylinder, spark-producing means associated with the cylinder for producing a spark therein, pressure-responsive explosionindicating means connected to. the cylinder for indicating occurrence of an explosion inthe cylinder, and means for varying the composition of said sample including a gas-measuring mem-' her for measuring a fixed volume of combustion inducing gas, said member having avalved connection at one end to one of said cylinder'con nections, and also having valved connection at its other end to the other of said cylinder connections and to a source of'combustion-ind'ucing gas. l' L j 11. Apparatusfor determining the explosibili ty of a gas comprising a cylindrical bomb provided with a valved inlet at one end and a valved outlet at the other end, means associated with the bomb for producing a spark therein, a pressure gauge connected to the inside of the bomb, and means for varying the composition of a sample of gas contained in said bomb comprising a tubular member of fixed volume provided at one end with valved connections to said outlet and to the atmosphere, and provided at the other end with a valved connection to a source of combustible gas and with a valved branch connection; and aspirating means associated with said inlet and adapted to be connected to said branch connection. 12. Apparatus for determining the explosibility of a gas comprising a bomb, means for producing a spark in the bomb including a spark gas associated with the bomb, a spark coil, and electrical connections between said gap and coil; a valved inlet and a valved outlet connected to the bomb, a switch forthe spark-coil circuit associated with said inlet to keep the spark cir' cuit open until the inlet valve is closed, a pres-. sure gauge connected to the bomb, aspirating meansconnected to said inlet, and means for cam displacingv a fixed incremental volume of a gas sample contained in said bomb by a like volume of a combustible gas comprising a tubular member provided at one end with valved connections to said outIetand to the atmosphere, and at thejother'fe'nd with a valved connection to a source of combustible gasand also with a valved branch connection adapted to be connected to said aspirating means.

13. 'Apparatus' for determining the explosibilityof a gas comprising a pressure-resisting gas sample container provided with closable inlet and outlet connectionsv for confining a sample of gaswithin the container, means for producing a spark within the container, pressure-responsive explosion-indicating means associated with the container, means for circulating a sample of gas in'a closed system including said container, and means for introducing a measured amount of a combustion inducing gas into said system.

.14. (A method of testing the explosibility of a gas which is not ignitible itself or in admixture with a combustible gas in an amount up to the lowerexplo'sive limit of saidcombustible gas, comprising confining a sample of said nonignitible gas in a closed system, admixing the sample with measured incremental amount of an oxygen-containing gas, exposing the mixture to ignition, and if the mixture does not explode, repeating such incremental dilution and exposure to ignition 'until' an ignitible mixture is obtained or 100% of oxygen-containing gas has been added. v

..15.v A me thod of testing the explosibility of a with a combustible gas in'an' amount up to the lower explosive limit of said combustible gas, comprising confining a sample of said nonignitible gas in a closed system under atmospheric, pressure, displacing an incremental volume'of the sample with an equal measured volumeof an oxygen-containing gas, exposing the mixture to ignition, and if the mixture does not explode, repeating such incremental dilution and exposure to ignition until an ignitible mixture is obtained or of oxygen-containing gas has been added.

'16. In a method of testing the explosibility of a gas, the steps comprising varying the compositionof a sample of said gas confined in a closed system by displacing an incremental amount of said sample with a like measured amount of a combustion-inducing gas, exposing the mixture to ignition, and if explosion does not occur, successively repeating such incremental variation until explosion occurs or 100 per cent of an explosion-produoing concentration of said combustion-inducing gas has beenadded.

.17."In a method of testing the explosibility of a gas, the steps comprising exposing to spark ignition a sample of said gas confined under atmospheric pressure in a closed system, and if explosion does not occur, displacing an incremental volume of-said sample with a like measured volume of a combustion-inducing gas, exposing the resultant mixture to ignition, and if explosion does not then occur, successively repeating such incremental variation in composition" until explosion occurs or 100 per cent of an explosion-producing concentration of said combustion-inducing 'gas has been added.

GEORGE W. JONES. 

